Okay, I’m confused, and I’m sure you are, too. Did you create a sidebar.php template file with the sidebar information that you want in there? If so, then it should show up on every template file that you put it on. If you have an archives.php template file, add it there.

See this line in the header.php:<?php /* Checks to see whether it needs a sidebar or not */ if ((! $withcomments) && (! is_single()) && (! is_page())) { ?>
and delete the single part:<?php /* Checks to see whether it needs a sidebar or not */ if ((! $withcomments) && (! is_page())) { ?>